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Ribosome run through of the termination codon in the absence of the ribosome releasing factor
Abstract:
The ribosome releasing factor (RR factor) which releases ribosomes from mRNA at the termination codon has been examined for its effects on the amino acid incorporation programmed by wild type R17 Phage RNA and amB2 R17 RNA. When RR factor was added at the beginning of the incorporation, there was no effect on the initial rate of incorporation but it reduced the final level of incorporation. The reduction of the final level of incorporation was more pronounced for histidine incorporation than for valine incorporation suggesting that the translation of the RNA polymerase cistron was more influenced by RR factor. These experiments were carried out under conditions where no reinitiation of protein synthesis occurred. In the presence of RR factor, suppressor tRNA functioned better for the incorporation of amino acids into proteins with amB2 R17 RNA than did wild type tRNA. No such differential effect of suppressor tRNA was observed in the absence of RR factor. This suggests that the ribosome has to be released from mRNA by RR factor in order for the amber mutation to be effective.
Insights
The ribosome releasing factor (RR factor) enhances suppressor tRNA function by releasing ribosomes from mRNA. This release is crucial for amber mutations to be effective during protein synthesis.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Ribosome releasing factor (RR factor) facilitates the termination of protein synthesis by releasing ribosomes from mRNA at stop codons.
- Understanding RR factor's role is key to deciphering translational control mechanisms and the impact of mutations.
Purpose of the Study:
- To investigate the effect of RR factor on amino acid incorporation programmed by wild-type and mutant R17 Phage RNA.
- To elucidate the interaction between RR factor, suppressor tRNA, and amber mutations during translation.
Main Methods:
- Amino acid incorporation assays using wild-type and amB2 R17 RNA.
- Experiments conducted with and without the addition of RR factor at the initiation of protein synthesis.
- Comparative analysis of suppressor tRNA and wild-type tRNA function in the presence and absence of RR factor.
Main Results:
- RR factor reduced the final level of amino acid incorporation without affecting the initial rate.
- The effect of RR factor was more pronounced on histidine incorporation, suggesting influence on the RNA polymerase cistron.
- In the presence of RR factor, suppressor tRNA showed enhanced function with amB2 R17 RNA, an effect not observed without RR factor.
Conclusions:
- Ribosome release from mRNA by RR factor is necessary for amber mutations to exert their effect.
- RR factor plays a significant role in regulating translation termination and influences the efficacy of suppressor tRNAs in specific contexts.